• Proceedings of the KIPE Conference
• /
• 2004.07b
• /
• pp.587-591
• /
• 2004

This paper proposes a novel current compensation technique that can eliminate the harmonic currents included in line currents without computation of harmonic current components. A current controller with fast dynamics for an active filter is described. Harmonic currents are directly controlled without the need for sensing and computing the harmonic current of the load current, thus simplifying the control system. Current compensation is done in the time domain, allowing a fast time response. The DC voltage control loop keeps the voltage across the DC capacitor constant. High power factor control by an active filter is described. All control functions are implemented in software using a single-chip microcontroller, thus simplifying the control circuit. Any current-controlled synchronous rectifier can be used as a shunt active filter through only the simple modification of the software and the addition of current sensors. It is shown through experimental results that the proposed controller gives good performance for the shunt active filter.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.12
• /
• pp.2065-2071
• /
• 2007

This paper suggests the harmonic effects on HTS(High Temperature Superconducting) power cable. HTS cable is regarded as not only one of the important countermeasure to supply high density power demand area, but also one of countermeasures greenhouse technology. However, with the development of digital society, the distribution line power is much contaminated with harmonics generated by various power electronic equipments. This paper describes how the HTS cable responds to the harmonic and increases AC losses caused by hysteresis phenomenon. EMTDC based harmonic simulation results are compared with AC loss measured values.

• KIEE International Transactions on Power Engineering
• /
• v.5A no.3
• /
• pp.235-243
• /
• 2005

Line constants of the catenary system are estimated. The harmonic current that the Korean Train Express (KTX) injects into the catenary is measured to precisely analyze the harmonic effects. The Korean high-speed railway system is modeled by estimated and measured results. The system model is applied for predicting the harmonic effects. The simulation results from the system model are compared to field test data concerning the total harmonic distortion (THD). The reliability of the system model is verified.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.49 no.10
• /
• pp.233-239
• /
• 2012

The harmonic frequency occurred in a power system causes errors and failures of equipments such as motors, and an unnecessary power consumption. The fundamental countermeasure for the harmonic frequency is to eliminate the cause of the harmonic frequency. This paper describes about making the device to figure out the cause in real time, verifying the operation of the device, and utilizing it to various power quality measurements. The power usually has the line frequency between 45Hz and 66Hz. In this research, the number of the harmonic frequencies which can be analysed inside the 2.8kHz bandwidth, the filter bandwidth of ADE7880, is 2800/f, and the maximum is 2800/45 = 63. The maximum order of the harmonic frequency in Korea, which has the line frequency of 60Hz, was measured as 2800/60 = 46th. Also, the accuracy of the voltage, current, and power measurement had the error within 0.1%, confirming that it is very precise.

• The Journal of the Acoustical Society of Korea
• /
• v.13 no.3
• /
• pp.71-77
• /
• 1994

The frequency characteristics of sound radiated by a line array of bubbles in water was investigated theoretically and experimentally. In the theory we proposed an effective coupled harmonic oscillator model for a line array of bubbles treating the interaction of only adjacent bubbles as the coupling of classical harmonic oscillators. For weak coupling of bubbles that the distance between adjacent bubbles is larger than the diameter of a bubble, the pressented theoretical model shows very good agreement with the experimental results.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.16 no.3
• /
• pp.259-269
• /
• 1991

In this paper, power line harmonic noise which is the most serious problem in the secondary power distribution line is eliminated and analyzed using adaptive noise cancellers with two adaptive algorithms, LMS and individual tap LMS(ITLMS) algorithm. To testify the improvement of data transmission characteristics made by the adaptive filter with two adaptive algorithms, BER was measured in DS spread spectrum communication system including the noise canceller.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.53 no.7
• /
• pp.397-404
• /
• 2004

This paper describes a study of transient characteristics in 765kV untransposed transmission lines. As the 765(kV) system can carry bulk power, some severe fault on the system nay cause large system disturbance. The large shunt capacitance and small resistance of 765kv transmission line make various difficulties for its protection. These problems including current difference between sending and receiving terminals on normal power flow, low order harmonic current component in fault current and current transformer saturation due to the long DC time constant of the circuit etc. must be investigated and solved. The analysis of transient characteristics at sending terminal has been carried out for the single phase to ground fault and 3-phase short fault, etc. The load current, charging current in normal condition and line flows, fault current, THD(Total Harmonic Distortion) of harmonics, time constants have been analysed for the 765kV untransposed transmission line systems.

• Proceedings of the KIPE Conference
• /
• 2003.11a
• /
• pp.90-94
• /
• 2003

Recently, many nations have released standard such as IEC 1000-3-2 and IEEE 519 which impose a limit on the harmonic current drawn by equipment connected to AC line in order to prevent the distortion of an AC line. Among the wide variety of active methods for improving power factor and harmonic distortion, the boost converter is very effective because it has a continuous line current , small choke filter and high power factor. In high power application, however, the bridge diode loss in the boost converter has made the efficiency lower and the temperature of the board higher. A new approach without bridge diode to make the same characteristics of the conventional boost converter has also been developed. This paper present the comparisons between the continuous current mode(CCM) operated conventional boost converter and the boundary current mode(BCM) operated the bridgeless boost converter for high efficiency and high power factor.

• Structural Engineering and Mechanics
• /
• v.66 no.3
• /
• pp.387-397
• /
• 2018

In this paper, a general closed-form solution for evaluating the dynamic behavior of a Timoshenko beam on elastic foundation under a moving harmonic line load is formulated in the frequency-wavenumber domain and in a moving coordinate system. It is found that the characteristic equation is quartic with real coefficients only, and its poles can be presented explicitly. This enables the substitution of these poles into Cauchy's residue theorem, leading to the general closed-form solution. The solution can be reduced to seven existing closed-form solutions to different sub-problems and a new closed-form solution to the subproblem of a Timoshenko beam on an elastic foundation subjected to a moving quasi-static line load. Two examples are included to verify the solution.

• The Journal of the Acoustical Society of Korea
• /
• v.27 no.4
• /
• pp.200-206
• /
• 2008

This paper presents a method of quantization to extract quantization parameters using the straight-line and DCT (Discrete Cosine Transform) for two splited frequency bands. As the number of harmonic is variable frame to frame, harmonics in low frequency band is oversampled to fix the dimension and straight-lines present a spectral envelope, then the discontinuous points of straight-lines in low frequency is sent to quantizer. Thus, extraction of quantization parameters using the straight-line provides a fixed dimension. Harmonics in high frequency use variable DCT to obtain quantization parameters and this paper proposes a method of quantization combining the straight-line with DCT. The measurement (If proposed method of quantization uses spectral distortion (SD) for spectral magnitudes. As a result, The proposed method of quantization improved 0.3dB in term of SD better than HVXC.